Generally, it is recognized that valves are useful for controlling the pressure of a fluid in a system. This is usually accomplished by providing means within the valve for reducing fluid pressure between the inlet and outlet sides thereof. However, such pressure reduction can generate an objectionable level of noise from the valve.
When reducing the pressure of a fluid in a system, noise may typically be generated by choking of the valve. Depending upon the environment in which the valve is used, the generation of such noise may be harmful to those persons exposed to it in terms of possible damage to their hearing and reductions in their work efficiency, but also such noise can have an adverse effect such as structural fatique and/or equipment malfunction relative to the system in which the valve is utilized. For instance, in industrial applications, noise generation from pressure reduction is clearly undesirable.
However, noise generation can be a critical problem in military applications. This is particularly true in high technology under water propulsion systems such as those used in torpedoes, submarines and the like. For such applications, a compact, quiet flow control valve having variable gain characteristics would be highly desirable.
When providing a flow control valve for military applications, it is also recognized that the valve should be reliable and effective. It is, therefore, essential not only that the valve reduce noise to a minimum, but also that it be relatively simple in construction so that the degree of pressure reduction can be achieved without multiple complex moving parts. While these requirements are known, it has remained to provide a highly effective variable gain valve having reduced noise generation characteristics.
Among the efforts to provide a silent operating valve is that disclosed in Parola U.S. Pat. No. 3,693,659, issued Sept. 26, 1972. Parola discloses a valve in which a concentrically positioned sleeve has openings therethrough which permits passage of fluid from an inner chamber through an annular porous member to an outlet by means of an axially movable inlet valve member positioned within the sleeve. However, Parola accomplishes the pressure drop primarily across the annular porous member rather than in an incrementally reduced manner.
An attempt to provide a porous element in a reciprocating member is disclosed in Huber U.S. Pat. No. 4,083,380, issued Apr. 11, 1978. It has also been proposed to utilize a porous metal disk contained within a spool to control flow between two outlets as disclosed in Armstrong et al U.S. Pat. No. 3,789,880, issued Feb. 5, 1974. Also, an attempt to provide stacked orifice plates in a fluid inlet of a pressure reducing valve is disclosed in Armstrong U.S. Pat. No. 977,427, issued Dec. 6, 1910.
Among other attempts to provide a flow control valve are those disclosed in U.S. Pat. Nos. 3,893,927; 3,631,891; 3,042,078; 2,918,087; 1,868,708; 1,224,221; and 462,823.
The present invention is directed to overcoming the above stated problems and accomplishing the stated objects.